TATE COLLEGE, Pa. - When Don R. Harrison Jr. was growing up in Philadelphia, neighborhood children would tease him and call him "white boy," because his skin was lighter than theirs. But Mr. Harrison, a "proud black man," was still unprepared for the results of a DNA test, taken as part of a class at Pennsylvania State University, to determine his genetic ancestry.

"I figured it would be interesting. I'm light-skinned and I wanted to know my whole makeup," said Mr. Harrison, a 20-year-old sociology major. But he was shocked by results showing him to be 52 percent African and 48 percent European: "which I had no clue about, considering both my parents are black," said Mr. Harrison. "So I'm half white."

Samuel M. Richards, who teaches Sociology 119, Race and Ethnic Relations, to 500 students each semester, said the DNA tests, which were conducted last year for the first time, were very popular with the class.

"Everyone wants to take the test, even students who think they are 100 percent one race or another, and almost every one of them wants to discover something, that they're 1 percent Asian or something. It's a badge in this multicultural world," he said.

About half of the 100 students tested this semester were white, he said, "And every one of them said, 'Oh man, I hope I'm part black,' because it would upset their parents.

"That's this generation," he said. "People want to identify with this pop multiracial culture. They don't want to live next to it, but they want to be part of it. It's cool."

The tests also help to deepen conversations about race, he said.

"When I teach I try to demonstrate to students how complex race and ethnicity are," Dr. Richards said. "My secondary goal is to improve race relations, and when people discover that what they thought about themselves is not true - 'I thought I was black, but I'm also Asian and white' - it leads them to have a different kind of conversation about race. It leads them to be less bigoted, to ask the deeper questions, to be more open to differences."

Mark D. Shriver, associate professor of anthropology and genetics at Penn State, took cheek swabs from about 100 student volunteers in Dr. Richards's class for the DNA tests.

Many students were surprised by the results of the test, which was created by Professor Shriver and his commercial partners at DNAPrint Genomics Inc. to measure genetic mixing in populations, because of the potential importance of racial or ethnic background to drug trials, and also because of the researchers' curiosity about their own ancestry. The company analyzed the test results free; the results will go into a database for Dr. Shriver's research.

The test compares DNA with that of four parent populations, western European, west African, east Asian and indigenous American, and the company claims it is more than 90 percent accurate.

Many unexpected results can be explained by family history. Mr. Harrison, for instance, recalled a great-grandfather who "would cross for white, he was so fair."

"The white women apparently found him attractive, and black women would flock to him because light was in back then." Mr. Harrison added, "He worked on the railroad, and he looked white in a black-and-white photo."

Natasha Best, a 21-year-old public relations major, has always thought of herself as half black and half white, because her mother is Irish-Lithuanian and her father West Indian. But the test proved her to be 58 percent European and 42 percent African.

"I was surprised at how much European I was, because though my father's family knows there is a great-great-grandfather who was Scottish, no one remembered him," said Ms. Best, who grew up in Yonkers. "I knew it was true, because I have dark relatives with blue eyes, but to bring it up a whole 8 percent, that was shocking to me."

But Professor Shriver explained that although a great-great-grandparent would contribute on average 6.25 percent of a person's genes, any one ancestor might be represented at a higher or lower level in today's generation.

Modern migration patterns are also leaving a mark. Ms. Best and Mr. Harrison are members of the fastest-growing ethnic grouping in the United States, one that was acknowledged in the 2000 census for the first time: mixed race. Yet the two students identify themselves in very different ways.

"I am 48 percent white - genetically I am, at least, but not culturally. And the fact that I'm black is more important, because it's something I know. It's who I'm comfortable with," Mr. Harrison said.

"Some people think it's funny that I consider myself Irish and celebrate St. Patrick's Day," Ms. Best said, "because no matter how you cut it, when you look at me you don't think, there goes a white girl."

She has noted discrimination on both sides. "Black people have told me I shouldn't date white people," said Ms. Best, whose boyfriend is white. Some of her white friends say their parents, too, disapprove of interracial dating. "Other people have told me I'm not really black, or I think I'm better than other black people because I'm lighter."

Mr. Harrison, who says that as a child he molded himself to be more black, does not want this new information to change his identity. "Just because I found out I'm white, I'm not going to act white," he said. "I'm very proud of my black side."

But whatever his genes say, or those of Ms. Best, they will most likely be seen as black - at least by white Americans - for the rest of their lives.

"I think the test is really interesting; I had to know," said Ms. Best. "But it makes me question, why are we doing this? Why do people, especially in this country, want to know? Why are we, as a people, so caught up in race? Maybe we haven't progressed as much as we thought we had."